Earphone Housing with Integrated Tuning Features

ABSTRACT

Custom in-ear monitors (headsets, headphones, earbuds, hearing aids) having improved audio fidelity characteristics and improved manufacturability are constructed by designing a virtual three-dimensional model housing including sound and vent tubes, and equipment mounting receptacles and clips; and fabricating the housing substantially simultaneously or all-in-one-go using, e.g., a 3D printer. The sound and vent tubes comprise features such as inflection points and profile variations that are impossible to construct using traditional subtractive manufacturing processes.

CONTINUITY AND CLAIM OF PRIORITY

This is an original U.S. utility patent application.

FIELD

The invention relates to electro-acoustic personal audio systems in thenature of headphones and earphones. More specifically, the inventionrelates to passive features of earphone housings that improve soundfidelity and manufacturing efficiency.

BACKGROUND

Traditional personal listening devices utilize one or more drivers asaudio reproduction sources. The sound waves from these drivers arecommonly carried from an enclosed, sub-miniature electro-acoustictransducer or driver, through a tube or sound bore connected thereto,and terminating at the tip of the canal portion of the device. In suchearphones, the device's overall frequency response is affected by thelength and inner diameter of the tubing or bores used to direct theoutput of the drivers to the earpiece or tip of the device. This use oftubing or bores is used to tailor the audio response of the drivers, butalso introduces tube resonance, affecting the frequency response of thedriver connected to the tubing or bore. Tubing or bores can alsoconstrict the sound waves passed from the driver through the tube orbore, often complicating the acoustic design of the device or exerting adeleterious effect on the overall fidelity of the system.

Alternate arrangements of transducers and other components in earphonescan simplify the design or construction of the device, or improve itssound-reproduction fidelity. These benefits may be of significant valuein this field.

SUMMARY

Embodiments of the invention are multi-driver in-ear monitors orearphones, where at least one driver delivers its sound waves through atube or bore formed together with a structural housing through which thetube passes.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows an earphone housing according to an embodiment of theinvention.

FIG. 2 shows a simplified view of a housing with sound bores.

FIG. 3 shows side and end views of a variety of sound bores according toan embodiment of the invention.

FIG. 4 shows an arrangement of drivers and housing bores according toanother embodiment.

FIG. 5 is a flow chart outlining a prior-art manufacturing method.

FIG. 6 is a flow chart outlining a manufacturing method according to anembodiment of the invention.

FIG. 7 is a flow chart highlighting certain distinguishing details of amanufacturing method of an embodiment.

FIG. 8 shows several views of the exterior of a housing constructedaccording to an embodiment.

FIG. 9 shows several views of the interior of the housing constructedaccording to an embodiment.

FIG. 10 illustrates simplified examples of distinguishing features of anembodiment.

FIG. 11 shows a hybrid embodiment comprising an inventive housingcombined with a prior-art casting.

DETAILED DESCRIPTION

Embodiments of the invention are in-ear monitors (also calledcanalphones and earbuds) with complex-shaped audio channels orpassageways and other features to improve assembly accuracy andmanufacturing efficiency.

FIG. 1 shows a sample earphone housing 100 according to an embodiment ofthe invention. The overall shape is designed to rest in a user's outerear, with a protrusion 120 that extends into the ear canal. The housingis partially hollow, leaving a space 110 that can contain audio drivers,microphones, electronic circuitry, and other components of a completeearphone. As described in greater detail below, embodiments arecharacterized by comprising a plurality of tubes or sound bores, shownin dashed lines at 130. These tubes carry sound waves from audiotransducers in the hollow space 110 through the protrusion 120 thatmates with the ear canal and into the airspace adjacent the user'seardrum. These areas of a user's anatomy are oddly-shaped, so actualembodiments are challenging to depict in simple line drawings.Simplified representations of embodiments are used when appropriate tohighlight the characteristics that distinguish an inventive earphonehousing from that which has gone before.

FIG. 2 shows a simplified view of an earphone housing 200 according toan embodiment of the invention. A housing typically has a hollow or openspace 210 which rests in or near the user's outer ear (auricle); thisspace can hold batteries, electronic circuitry, electroacoustictransducers (drivers, speakers) and other components of an in-earmonitor or hearing aid. The open space often has a cover, though this isnot shown in this Figure. Adjacent to this outer portion is a protrusion220 which is shaped to fit snugly into the user's ear canal,substantially sealing the ear canal to prevent sound from entering fromoutside. The protrusion often has a complex shape, corresponding to thecomplex shape of the ear canal, but in this simplified depiction, it isshown as a rectangle.

Two channels, or bores, are shown passing through the protrusion fromthe hollow space 210 to an enclosed airspace inside the user's earcanal, adjacent his tympanic membrane (eardrum). These channels allowsound waves created by a transducer located in the hollow, outer portionof the monitor to pass through the protrusion and be heard by the user.

In the prior art, channels were formed by drilling or grinding throughan often-solid, molded protrusion. This technique restricts the numberand configuration of the channels to ones that can be reached from oneend or the other by a straight rotary tool (230, 240). A distinguishingcharacteristic of an embodiment of the invention is a passageway throughthe protrusion having a portion that is not accessible by a straightrotary tool from either end of the passageway, as shown at 250, 260 and270: the portion of the passage at 270 cannot be reached by a straighttool from either end of the passage. Another way of expressing thischaracteristic is that the centerline of passage 250, 260, 270 has aninflection point near the middle of segment 270 where the centerlinecurvature changes from positive to negative (that is, the bend changesdirections). In the prior art, such a passage could be possible to makeand if it was attempted to be made in two parts, this approach quicklyreaches its limits for multiple passages, or passages that curve or bendin another orthogonal direction, are desired.

The channels, tubes or sound bores of an embodiment may take a varietyof shapes, some examples of which are shown in FIG. 3. A straight,uniform-diameter circular bore 310 is the simplest of these. Bores maybe simply curved with a round profile, 320, or may have complex curves330 with inflection points 335 where curvature changes from positive tonegative.

A tube may decrease in diameter linearly, like a truncated cone, orincrease with a curve like a trumpet, 340. The tube may have enlargedportions along its length, 353, and/or may have a non-circular profile356.

To fit more bores in a small-diameter ear canal, a plurality of tubesmay be placed along a common axis 360; such tubes may be separated fromone another along their run by very thin and roughly even partitions.Such pluralities of tubes are called “bore groups.” Tubes in a boregroup may be of approximately equal sizes, as shown at 365, or may be ofdifferent sizes. Tubes may subdivide or split along their length, 370.

Note that FIG. 3 shows tubes bending and changing sizes in only twodimensions. It should be understood that an embodiment is athree-dimensional structure, and so tubes may bend and change sizes inany direction.

In an embodiment, combinations of these bore features can be used toadjust the length and volume of each bore, which allows its acoustic andpneumatic characteristics to be controlled precisely. For bores that arenot intended to carry sound (e.g., vent tubes), the flexibility inplacing and sizing the channels allows them to avoid other elementswhose size or placement is important to the acoustic performance of thedevice.

FIG. 4 shows some features of an earphone housing that can improvemodularity and assembly ease. An electroacoustic transducer (driver,speaker) 410 may be received as a sealed module having a cylindricalspout 415 through which sound is emitted. An earphone housing accordingto an embodiment may have a sound bore 420 sized to couple directly tothe spout (i.e., a “socket” for the spout). The housing may alsocomprise clips, dividers or guide partitions 430 to hold driver 410 inplace against the sound bore 420. Assembly of such an embodiment may besignificantly accelerated over a prior-art earphone where drivers mustbe manually aligned and cemented in place. In a multi-driver earphone,another driver 440 may be connected to its sound bore 450 by a flexibletube 460. The outer diameter of the tube 463 may match the diameter atone end of bore 450, as shown at 470. The sound bore diameter may have asharp discontinuity near the surface, so that the inner diameter 455 ofthe bore beyond the discontinuity matches the inner diameter of the tube465.

Earphone housings according to embodiments of the invention may befabricated using equipment and techniques commonly known as “3DPrinting.” In 3D printing, a virtual model of the desired structure isprepared using solid modeling and computer-aided design techniques andsoftware. Then, the model is transmitted to a fabrication device, whichcreates an object that substantially matches the surfaces, volumes andvoids of the virtual model. The process can be thought of as reducingthe model to a three-dimensional array of small cubic volumes(“voxels”), which may either be empty or contain the material of thehousing. The 3D printer may replicate the model by fusing togetherparticles or melted drops of a thermoplastic material such as nylon, ABSor PLA, or by solidifying selected portions of a photosensitive resin.Since 3D printers build up structures layer by layer, complex soundbores and other features may be constructed, even though such featureswould be difficult or impossible to create by standard plastic moldingtechniques or by removing material from a solid workpiece (subtractivemachining such as CNC). An earphone housing according to an embodimentwill include sound bores and other channels whose interior surfacessubstantially match those of a virtual model stored on a non-volatilecomputer-readable medium of a computer.

In the prior art (FIG. 5), custom-fit earphones were constructed byintroducing a viscous, self-hardening material into the user's outer earcanal and auricle (510). Once the material sets, it can be extractedfrom the ear (520), and serves as a model of the outer surface of thecustom-fit earphone. A negative mold is made from the model (530), andthen a copy of the model is cast in the mold from a suitablebiocompatible material, such as a thermoset plastic or polymerized resin(540).

Material is removed from the copy by drilling and grinding, leaving justa shell whose outer surface complements the user's outer ear canal andauricle (550). Suitable audio reproduction equipment (audio drivers,electronic frequency crossovers, batteries, etc.) is installed in theshell (560). Finally, a cover may be placed over the audio reproductionequipment to protect it (570), and the custom-fit earphone is complete.

Step 550, removing material from the cast copy, is often done bytime-consuming, manual grinding and drilling. This process also limitsthe number of bores that can be safely drilled without compromising thestructural integrity of the shell. Errors during this operation maydamage or destroy the cast copy, requiring a new copy to be cast.Custom-fit earphones manufactured according to an embodiment of theinvention may improve yield and reduce time, as explained with referenceto FIG. 6.

As in the prior art, a self-hardening material is used to construct amodel of the user's outer ear canal and auricle (610). Next, the modelis scanned to produce a virtual model—a data set describing the size,shape and contours of the model surface (620). Standard 3D modelingtechniques are used to “hollow out” this virtual model (630), leavingwalls of suitable thickness. The portion of the virtual model thatextends into the user's ear canal (also referred to in this disclosureas the “protrusion”) may be left mostly solid.

Still working with virtual-model dataset, representations of the audioreproduction equipment (e.g., audio drivers or speakers, includingwithout limitations balanced-armature drivers) are positioned atsuitable locations within the virtual model shell (640). Audio channelsare laid out in the virtual model (650) so that when the virtual modelis fabricated and audio equipment is installed, the sound waves cantravel from the drivers, through sound bores traversing the protrusionto reach the user's eardrum. The audio channels may includecharacteristics like those described with reference to FIG. 3, so thatthe length, diameter, volume and other parameters match the desiredaudio performance of the drivers to be installed. In particular, aplurality of channels (a “bore group”) may be placed adjacent each otheralong a common lengthwise axis, so that each channel is spaced apartfrom its neighbors. Channels in a bore group may be of equal size, or ofunequal size.

Since this part of the process is still working with a virtual model,errors such as audio channels piercing the model surface at incorrectlocations can easily be corrected. Furthermore, audio channel featuresthat would be difficult or impossible to form by subtractivemanufacturing techniques (e.g., grinding, milling or drilling a solidmodel) can be specified in the virtual model dataset.

Next, the virtual model is transmitted to a 3D printer which fabricatesthe housing of the earphone (660). During this fabrication step, thecomplete housing (shell, protrusion, tubes, sound bores, equipmentmounting clips and other features) are formed substantiallysimultaneously or all in one go—3D printers typically build up an objectas a series of layers over a few minutes, and there is often little orno post-fabrication modification required to arrive at a finished piece.For purposes of this disclosure, “substantially simultaneousfabrication” refers to the fabrication of an earphone housing by aprinter or similar device in a single, brief manufacturing operation.

Drivers and other audio equipment are installed (670) and a cover may beadded (680) to produce a finished earphone. In some embodiments, thehousing fabricated by the 3D printer may, in use, contact the skin ofthe user's ear directly, while in other embodiments, a durable coatingmay be applied over the outer surface of the housing.

FIG. 7 is another outline of a process by which an embodiment can bemanufactured. This flow chart focuses on several distinguishingcharacteristics of the process. As before, it begins with the making ofa casting of the user's outer ear canal and auricle (710). This castingis scanned to produce a virtual model (720). The model may be simplifiedand cleaned up, and the portion that lies outside the ear canal ishollowed out (operations not shown).

Next, a plurality of sound and vent tubes are positioned within thevirtual model (730). Tubes intended to carry sound waves may becarefully sized and positioned so that they have the desired audiotransmission characteristics. For example, they may be laid out withbends or size or profile changes not required to fit within the outerboundaries of the model, but made so that the length or enclosed volumeof the tube is suitable for the range of frequencies the tube isintended to carry from a driver to the user's ear canal. Vent tubes,which are not intended to carry sound waves, may be laid out with lessconcern for length or volume, since the air within them is essentiallystatic compared to the sound waves in the sound tubes.

Turning briefly to FIG. 10, note that the sound and vent tubes may passthrough an otherwise solid portion of the housing (e.g., the protrusionthat enters the user's ear canal, 1010), or they may pass through anopen portion of the housing shell 1020 that rests in the user's outerear. Tubes may adjoin or follow the inner surface of the housing shell1030, or they may be free-standing 1040, supported only on the ends orat intervals along their length. Some tubes may be connected to thehousing shell or other support structures therein by solid or perforatedwebs formed with the housing 1050.

Returning to FIG. 7, the virtual model is modified by “subtracting” thesound and vent tubes (740). This is a Boolean operation that changes thevirtual model so that, when fabricated, housing material will be omittedfrom the areas where the tubes were positioned. Thus, the virtual modelrepresents a structure through which channels have been bored.

During this virtual design process, blocks representing audio driversand other components to be installed in the housing are positionedwithin the model (750). To simplify later assembly, spring clips mayalso be designed into the housing (760)—since the housing material isflexible and resilient, clips to hold audio drivers and other componentsmay be formed from the same material, at the same time as the rest ofthe housing is manufactured.

Once all the sound tubes, vent tubes, audio-driver receptacles, securingclips and other features have been laid out in the virtual model, datarepresenting the model is transmitted to a 3D printer which fabricates aheadphone housing that is very similar to the virtual model (770). (Inmany workflows, the data may be stored on a computer-readable medium forfuture reference, and then a copy of the data may be transmitted to aprinter.) Finally, the audio drivers, electronics, vent filters andother components are installed into the housing to complete theheadphone (780). Preferably, at least some of the audio reproductionequipment can be installed and held in place solely by receptacles andclips formed directly in the material of the housing, without requiringadhesives, screws or other assembly aids. It is appreciated that auser's left and right ears may not be mirror images of each other, so acomplete custom stereo headset may require two similar but notmirror-image housings to be designed and fabricated.

FIG. 8 shows several views of an example headphone housing constructedaccording to an embodiment of the invention. As can be seen, the outershape is quite complex, with bumps, lobes and depressions correspondingto the shape of the user's ear. The protrusion that extends into theuser's ear canal is circled at 810, while the adjacent portion is sizedand shaped to rest in the user's outer ear. The ends of several soundand vent tubes are visible at 830, at the end of the protrusion 810. Thehousing may have openings such as 840 formed therein, to acceptconnectors or pass-throughs to connect to equipment installed inside thehousing.

FIG. 9 shows additional views of the same example headphone housing. Theprotrusion is visible in one of these views at 910, and the hollow areawhere audio drivers and other components may be installed is at 920.Although the portion of the housing that rests in the user's outer earhas a very complex shape, the virtual-model designing tools can ensurethat the hollow portions of the shell have a uniform wall thickness 930.The large hole at 940 in this embodiment is a receptacle for a ventfilter similar to that disclosed in co-pending, commonly-ownedapplication Ser. No. 15/425,881. A free-standing vent tube, visible at960, connects this receptacle through the protrusion 900 to one of theholes visible in FIG. 8 at 830. The ends of three sound tubes are alsovisible at 950; these tubes also pass through the protrusion and exitwithin the user's ear canal. Finally, notch 970 is sized and shaped toaccept an electrical connector when the audio reproduction equipment isinstalled into the housing. The sample housing depicted here does notinclude the audio-driver clips because they would complicate theillustration and make it difficult to understand.

In a preferred embodiment, instead of scanning, arranging and printing afully-custom earphone housing for each user, a small number ofstandard-sized housings may be pre-designed, with audio equipmentinstallation receptacles placed for efficient assembly, and soundchannels routed for optimum audio performance. These standard-sizedhousings (e.g., small, medium and large versions, or versions withthree, six, nine or twelve audio drivers) may be fabricated,pre-assembled, and used as a single monolithic component in a prior-artcasting process. Note that, according to an embodiment of the invention,these standard-sized housings will nonetheless comprise complex soundand vent tubes including inflection points, bore groups, profile changesand so forth, and also clips and receptacles for installing audioequipment. This complexity arises because there is not much room in anyuser's ear canal and outer ear for all of the equipment needed in theearphone. Thus, even though the outer surface of a standard-sizedhousing does not closely complement the folds and depressions of anyparticular individual's ear, the housing is designed to occupy most ofan ear of the particular size (small, medium or large) and to provide asmuch room as possible for equipment such as drivers, electroniccrossovers, amplifiers, wireless receivers, batteries and so forth. (Notall headphones will contain every type of equipment.)

With such a standard-sized housing, instead of casting a solid model ofthe user's ear (FIG. 5, 540) and using subtractive machining processesto open spaces to hold the audio equipment (550), the pre-fabricated,pre-assembled standard-sized component may be cast directly into themold constructed from the custom impression of the user's ear. Thisapproach marries the improved manufacturing characteristics and improvedaudio performance of an embodiment with the custom fit of a prior-artearphone. FIG. 11 shows such a hybrid embodiment at 1100: 1110 (shown indashed outline) is a standard-sized monolithic housing componentcontaining audio drivers and other equipment, with complex soundchannels according to an embodiment to carry audio from the driversthrough the protrusion to the orifices 1140 near the user's eardrum. Asecond standard-sized monolithic housing 1120 may be positioned adjacentthe first housing 1110; this housing may contain batteries, electronics,wireless transceivers, or other components of a headphone. By splittingthe standard-sized housings into multiple parts, the parts can berepositioned if necessary to fit in the space available in a particularuser's outer ear.

The standard-sized housings 1110, 1120 are cast into a mold of theuser's ear, so that the outer surface of the completed earphone (e.g. at1130) closely complements the user's ear. This outer casting ensures asecure, close fit, which helps keep the earphone from falling out, andreduces the impact of extraneous noise on the audio reproduced by theearphone drivers and electronics.

The applications of the present invention have been described largely byreference to specific examples and in terms of particular arrangementsof components and structures. However, those of skill in the art willrecognize that earphones comprising complex, 3D-printed housings thatinclude sound tubes, vent channels, equipment mounting receptacles andclips, and other features described above, can also be constructed bymethods and techniques that vary from the foregoing description. Suchvariations and alternate techniques are understood to be capturedaccording to the following claims.

We claim:
 1. A method of manufacturing a housing for an in-ear monitor,comprising: selecting a number of bores for a bore group, said numberlarger than one; positioning a lengthwise axis of the bore group withina virtual model of a housing for an in-ear monitor; automaticallyplacing the number of bores adjacent the lengthwise axis along itslength so that each bore is spaced apart from its neighbors; computing aBoolean difference between the virtual model of the housing and theautomatically-placed bores to produce a bored virtual model; andfabricating a housing for an in-ear monitor by fusing together voxels ofa thermoplastic material to match the bored virtual model.
 2. The methodof claim 1, further comprising: setting a size for at least one bore ofthe bore group, said size being different from a size of at least oneother bore of the bore group.
 3. An audio reproduction devicecomprising: a housing; and a plurality of electroacoustic driversdisposed within the housing, wherein at least one electroacoustic driverof the plurality of electroacoustic drivers is coupled to a sound boreformed within the housing, and wherein a configuration of the sound borewithin the housing substantially matches a virtual model of the housingincluding a virtual model of the sound bore, said virtual model storedon a tangible, machine-readable medium and used during fabrication ofthe housing.
 4. The audio reproduction device of claim 3, furthercomprising: a vent bore formed within the housing, and wherein thevirtual model of the housing further includes a virtual model of thevent bore.
 5. The audio reproduction device of claim 3, furthercomprising: a mounting clip or feature to hold at least oneelectroacoustic driver of the plurality of electroacoustic drivers in apredetermined position without adhesive or auxiliary mechanicalfasteners.
 6. The audio reproduction device of claim 5 wherein themounting clip or feature comprises a spring clip formedcontemporaneously with and from a same material of the housing, saidspring clip operative to hold the at least one electroacoustic driver ofthe plurality of electroacoustic drivers in the predetermined positionwithout adhesive or mounting hardware.
 7. The audio reproduction deviceof claim 3, wherein the sound bore comprises a segment that cannot beaccessed by a straight probe from any external opening of the soundbore.
 8. The audio reproduction device of claim 3, wherein the soundbore comprises segments of varying cross-sectional area, where a segmentof larger cross-sectional area lies between segments of smallercross-sectional areas.
 9. The audio reproduction device of claim 3,wherein the sound bore divides into a plurality of bores along itslength.
 10. The audio reproduction device of claim 3, wherein a portionof the sound bore adjoins an inner surface of the housing.
 11. The audioreproduction device of claim 3, wherein a portion of the sound bore isspaced apart from an inner surface of the housing, said spaced-apartportion connected to the inner surface of the housing by a support web.